Conventionally, such a substrate transfer apparatus is equipped in a processing apparatus for processing a substrate such as a semiconductor wafer or the like. A semiconductor wafer inspection apparatus will be described as one example of the processing apparatus. The inspection apparatus includes a probe chamber for inspecting electrical characteristics of a semiconductor wafer and a loader chamber arranged adjacent to the probe chamber. The probe chamber includes a movable mounting table for supporting the semiconductor wafer, a probe card arranged above the mounting table and an alignment mechanism for aligning a plurality of probes of the probe card with a plurality of electrode pads of the semiconductor wafer.
After aligning the semiconductor wafer, the inspection apparatus performs specific inspection by bringing the semiconductor wafer into electrical contact with the probes of the probe card. The loader chamber includes a receiving part for receiving a plurality of semiconductor wafers on a cassette basis therein and a substrate transfer apparatus (hereinafter referred to as a “wafer transfer apparatus”) having a pincette that transfers each of the semiconductor wafers between a cassette and the probe chamber. The semiconductor wafers accommodated in the cassette are taken out sheet by sheet, pre-aligned and transferred to the probe chamber by means of the pincette. After the inspection, the inspected semiconductor wafers are transferred from the probe chamber to their original positions in the cassette.
The pincette is formed as an attracting body for attracting and holding a semiconductor wafer. As examples of the attracting body, there are known a vacuum chuck for vacuum-attracting a semiconductor wafer and a Bernoulli chuck for attracting and holding a semiconductor wafer according to Bernoulli principle, the latter which is disclosed in Japanese Patent Laid-open Publication No. H8-203984. The vacuum chuck is designed to attract and hole the bottom surface of the semiconductor wafer, whereas the Bernoulli chuck is configured to attract and hole the top surface of the semiconductor wafer.
There is a tendency that semiconductor wafers are becoming thinner for the reason of which the semiconductor wafers are apt to be warped or cambered. Therefore, when a plurality of semiconductor wafers W is received in a cassette 1 in a vertically spaced-apart relationship with one another as shown in FIG. 5, it is sometimes the case that a downwardly cambered semiconductor wafer and an upwardly cambered semiconductor wafer are adjacently placed one atop the other within the cassette 1. In this case, it is impossible to insert a conventional pincette 2 between the upper and lower semiconductor wafers because no gap is left therebetween.
Therefore, one of the upper and lower semiconductor wafers cannot be taken out from the cassette 1. Further, although not shown in the drawings, three pins which are movable up and down are provided in a mounting table and the semiconductor wafer is transferred to/from the mounting table by the pincette in a state that the pins protrude above a mounting surface. Therefore, when the semiconductor wafer to be transferred from the mounting table by the pincette is warped in a downward direction, it is often the case that the pincette cannot be inserted between the semiconductor wafer and the mounting surface if the pincette is a vacuum chuck. In this case, the pins need to be lengthened so that a pincette insertion gap which is large enough to insert the pincette can be created between the semiconductor wafer and the mounting surface.